The present invention claims priority under 35 U.S.C. .sctn..sctn.119, and 120 based upon an application in the United States Patent & Trademark Office on 7 Apr. 1992, assigned Ser. No.:07/864,941, and an application filed in the Korea Industrial Property Office on 30 Aug. 1991, assigned Ser. No.:1991/15149.
The present invention relates to a magnetic recorder/reproducer, such as a tape recorder or a video player, and particularly to a tape back-tension mechanism wherein a constant tension is applied to a tape travelling in the counter-clockwise direction during review and rewind modes.
Generally, in magnetic recorders/reproducers, such as tape recorders and video players, when a tape cassette, having a magnetic tape therein, is seated on a supply reel table and a take-up reel table, the magnetic tape is loaded and is placed in close proximity to the outer periphery of a head drum. Also, in accordance with the operational mode, an idler gear selectively engages either the supply reel table or the take-up reel table. That is, the idler gear engages the take-up reel table during the play and fast-forward modes, thereby making the tape travel clockwise. Alternatively, (during review and rewind modes), the idler gear engages the supply reel table, making the tape travel counter-clockwise.
However, while the tape travels in a selected direction by the rotation of the selected reel table, the tape is loosened due to the inertia of the unselected reel table's rotation.
Accordingly, the tape becomes loose at the outer periphery of the head drum during the review mode, which causes noise. Moreover, since the tape is excessively drawn out from the unselected reel table during the rewind mode, noise occurs, and the tape may become tangled within the recorder/reproducer. In order to prevent such problems, a weak back-tension may be applied to the tape while the tape travels in the review or rewind mode. To provide the weak back-tension, a weak brake is installed, wherein the weak brake applies a force to the reel table which is not driven by the idle gear. In addition, the weak brake is not driven by the idler gear.
FIG. 1 is an art published in the U.S. Pat. No. 4,899,951, illustrating a braking system having a weak brake for putting a back-tension on a magnetic tape. Here, a cam gear 1 has an irregularly formed slot 2, and a roll follower 4 is inserted into slot 2, to be slid along the irregularly formed slot. Roll follower 4 is coupled to one arm of a Y-shaped brake-releasing member 3. Brake-releasing member 3 is fixed to be rotatable about a pivot 3a, and drawn toward the unreleased direction (clockwise) by a spring 3b. Due to this connection, roll follower 4 is maintained in slot 2 of cam gear 1. Brake releasers 3s and 3t are fixed on the other arm of brake-releasing member 3. Brake releasers 3s and 3t are connected to a reel brake 5s of a supply reel 7s and a reel brake 5t of a take-up reel 7t, respectively.
Also, brake releaser 3s is coupled with a weak brake 6, and fixed on a pivot 5a, coaxial with reel brake 5s. Reel brake 5s of supply reel 7s and reel brake 5s of take-up reel 7t are rotated about pivots 5a and 5a', respectively, and kept under pressure by springs 5b and 5b', respectively, thus counteracting the rotation of reels 7s and 7t, respectively. In the same manner, weak brake 6 is kept under pressure by spring 6a, to counteract the rotation of supply reel 7s.
FIG. 1 shows the fast-forward mode of the system's operation. As cam gear 1 is rotated clockwise, brake-releasing member 3 rotates counter-clockwise. Then, reel brakes 5s and 5t are released, and accordingly, only weak brake 6 applies a gentle braking force to supply reel 7s. As a result, back-tension is provided to the tape during the fast-forward mode due to the braking force of weak brake 6, thereby preventing the tape from being drawn out.
However, the brake system with the weak brake apparatus having the above structure requires many parts to selectively operate weak brake 6 according to respective modes. That is, a driving source is separately required for driving the cam gear. Further, a cam gear with an irregularly shaped slot, as well as a brake-releasing member connected to the cam gear, are also required to operate the weak brake in accordance with the cam gear's rotation.
Therefore, the apparatus is complicated in its structure, and requires excessive space for installation, so that its manufacture and assembly become overly fastidious. These drawbacks, in turn, lead to deterioration of operation and degraded accuracy for the end product.